The present invention concerns a process and device for the training of human vision. In particular, the invention relates to a process and apparatus by which a change of the visual performance of persons in need of a training for improvement or completion of their vision can be affected by stimulating their visual system with optical stimuli.
Impairments of a human""s visual system may either result from an incomplete or impaired development of the visual system during infancy or from a deterioration either continuously and naturally due to ageing of the person or more or less abruptly due to diseases or accidents more or less severely influencing the visual system. It was, for example, found that the vision of children can substantially be improved by regular sessions of training their visual system, e. g. in cases of squinting. On the other hand, persons whose vision was deteriorated for any reason may either stop the deteriorating development or even improve their vision by a specific training adapted to the cause of deterioration of their visual system. The present invention intends to provide a process and device for training and improving a human""s vision in all conceivable cases of impairment where the presentation of optical stimuli to the visual system of a person having need for an improvement of the vision may promise a successful removal of the cause of impairment and/or increase his/her performance.
In recent years computer-technology has been utilized to train mental functions of the human brain. For example, the prior art reports on methods to treat temporal processing deficits of language-learning impaired children using computer-training as a paradigm (M. M. Merzenich et al., Temporal processing deficits of language-learning impaired children ameliorated by training; Science 271, 77-81 (1996)). It is not clear, however, whether computer-based training can facilitate other sensory modalities such as visual functions after damage to the brain.
Brain injury, which may result from stroke or trauma, often impairs visual functions. Patients typically loose sight in one half of the visual field while the other side often remains unimpaired. This partial blindness is generally considered untreatable because it is the long-held belief that proper vision requires a highly specific neuronal organization (D. H. Hubel, T. N. Wiesel, Receptive fields, binocular interaction and functional architecture in the cat""s visual cortex, J. Physiol. 106-154 (1962)). Despite this specificity in neuronal organization, there is, however, a considerable degree of plasticity in the injured visual system (U. Eysel, O. J. Gruesser, Increased transneuronal excitation of the lateral geniculate nucleus after acute differentiation, Brain Res. 158, 107-128 (1978); J. H. Kaas et al., Reorganization of retinotopic cortical maps in adult mammals after lesions of the retina, Science 248, 229-231(1990); C. D. Gilbert, T. N. Wiesel, Receptive field dynamics changes in adult cerebral cortex, Nature 356,150-152 (1992)). Lost visual functions can recover spontaneously to some extent in animals (J. Sautter, B. A. Sabel, Recovery of vision despite progressive loss of retrogradely labelled retinal ganglion cells after optic nerve crush, Europ. J. Neurosci. 5,680-690 (1993); B. A. Sabel, E. Kasten, M. R. Kreutz, Recovery of vision after partial visual system injury as a model of post-lesion neuroplasticity, Adv. Neurol. 73, 251-276 (1997); T. N. Wiesel, D. H. Hubel, Extent of recovery from the effects of visual deprivation in kittens, J. Neurophysiol. 28, 1060-1072 (1965); K. L. Chow, D. L. Steward, Reversal of structural and functional effects of long-term visual deprivation in cats, Exp. Neurol. 34, 409-433 (1972)) and man (H. - L. L. Teuber, W. S. Battersby, M. B. Bender, Visual field defects after penetrating missile wounds of the brain, Cambridge, Mass., Harvard University Press (1960)). At least some of this spontaneous post-lesion neuroplasticity of the adult visual system is due to extensive receptive field reorganization following lesions in retina or cortex (U. Eysel, O. Gruesser, loc. cit.; J. H. Kaas et al.. loc. cit.).
In the prior art, training methods have been disclosed that can be used to improve visual functions of brain damaged monkeys (A. Cowey, Perimetric study of field defects in monkeys after cortical and retinal ablations, Quart. J. Exp. Psychol. 19, 232-245 (1967)) and of men (J. Zihl, Zur Behandlung von Patienten mit homonymen Gesichtsfeldstxc3x6rungen, Z. Neuropsychol. 2, 95-101 (1990); E. Kasten, B. A. Sabel, Visual field enlargement after computer training in brain damaged patients with homonymous deficits: an open pilot trial, Restor. Neurol. Neurosci. 8, 113-127 (1995)). However, in humans it has not generally been accepted that training can improve vision. Nevertheless, several observations were made that suggest that humans with visual system damage may benefit from visual training.
The first observation that visual training may be effective in humans is the study by Zihl et al. (loc. cit.), who found that repeated presentation of visual stimuli and measurements of incremental thresholds in the same retinal location results in small expansions of visual field borders in persons with visual field defects. Repeated testing in this situation requires, however, an experimenter to carry out the training with the person to be trained, i.e. this method cannot be used by the person independently. Thus, it is extremely time consuming for both the person and the experimenter.
To overcome this manual approach of presenting visual stimuli, several devices have been disclosed in the prior art with which automated testing can be achieved. Although their efficacy has only been shown in a few individual persons and a strictly planned clinical trial was never carried out, there have been claims that these methods may improve visual functions. However, because these prior art devices have been too complicated to use and inefficient in their application, they have not been widely accepted in clinical practice.
In the document No. DE-U 93 05 147 issued to Schmielau, for example, a device for training the visual system of humans is described consisting of a large size hemispheric half bowl. Here, arrays of small light bulbs are positioned in a large diameter semicircle. Light stimuli are presented by illuminating sequences of said light bulbs arranged closely to each other such that they may stimulate the visual field in different excentricities from the center which has to be visually fixed. While this device does allow assessment and training of the entire visual field in its full extent, it has several disadvantages which preclude its widespread use. The disadvantages are (1) its size, (2) the inflexible position with which visual stimuli can be presented, and (3) the absence of any teaching of orienting the training according to the residual visual functions. Due to the lack of presentation strategy, the use of the Schmielau prior art device requires extended time periods. In addition, the half bowl used for training is inpracticable for home use.
The limitation of the Schmielau invention is apparent from the FIG. 4 of said document: There, as also described in the classical text books, the visual system of a human is shown by areas which are either intact or deficient. There is no mention of areas of impaired, residual visual functions based on which a visual field training may be performed.
One may presume that computers might be useful to replace such a large size, unpracticable device, but Schmielau (loc. cit.) states that this is not possible.
Therefore, since it is clearly stated that computer controlled training is not useful for purposes of visual field training, the use of computers was always refused in the prior art by those skilled in the art.
In contrast to the general expectations in the art, we have surprisingly found that a computer-controlled training procedure for visual functions of a human can contribute considerably to an improvement of the training effect. There was, therefore, developed a computer program which has been described elsewhere (E. Kasten, B. A. Sabel, Visual field enlargement after computer training in brain damaged patients with homonymous deficits: an open pilot trial. Restor. Neurol. Neurosci. 8, 13-127 (1995)). The principle advantage of using a computer-controlled device is that it is much smaller and that it allows the continuous recording of the person""s performance. However, the programs described by Kasten et al. (loc. cit.) present the stimuli in random order on a computer screen, without considering the person""s actual performance in the visual task. Therefore, training has been time consuming and inefficient, though this method has been shown effective in an early pilot study.
In the paper published by Kasten et al. (1997; loc. cit.) the program has been described. xe2x80x9cSehtraxe2x80x9d, for instance, presents small light stimuli of variable luminance in all parts of the visual field, but it does not adapt to the person""s actual performance in the different field sectors. It is noted that the stimuli are presented at random by a predetermined sector of the monitor to the person""s visual field, without considering the actual nature of the deficit and the zone of partial Visual system injury or residual visual function (so-called xe2x80x9ctransition zonexe2x80x9d).
Because of this, the persons to be trained have to respond to stimuli addressing areas of their visual field which are, in fact, intact. As a consequence, much time is spent by the person for purposes which are useless therapeutically. This situation produces an unnecessary demand on the person""s time and patience. Boredom and loss of motivation has therefore often been observed.
In order to overcome this limitation, it was an object of the present invention to provide a process and device for the training of human vision, which avoid the known disadvantages of the prior art. In addition, it was an object of the invention to provide a process and device for the training of human vision which take into account the training of zones of the person""s visual system where residual visual functions are maintained or where the natural vision is partly deteriorated only or where the natural vision is to be maintained on a high quality level (so-called xe2x80x9ctransition zonesxe2x80x9d). It was a further object of the invention to provide a process and device for the training of human vision which allow an extension of the person""s visual field into said transition zone and of said transition zone into a zone of substantially complete visual system injury in the case that the vision of a person is severely injured. In addition, it was an object of the invention to provide a process and device for the training of a human""s vision which may be handled not only in usual training centers under the supervision of an experienced experimenter but also in the person""s private environment by himself.
Surprisingly, the above objects were achieved by the present invention. The inventors conceived a new manner by which visual stimuli are presented on a simple device for emitting optical stimuli to the visual system of a human.
In a very general sense, the invention relates to a process for training the visual system of a human by presenting optical stimuli to said human, said stimuli being presented to a zone within the intact visual field of said human and to a zone outside the intact visual field of said human, the latter zone comprising a zone to be trained, thereby allowing an improvement of the vision in said latter zone, said process comprising the steps of
locating and defining a zone of deteriorated vision or residual visual function or partial visual system injury (xe2x80x9ctransition zonexe2x80x9d) within the human""s visual system;
defining a training area which is located within said transition zone;
training the human visual system by presenting visual stimuli to the human visual system, the majority of said visual stimuli being presented in or near said transition zone;
recording changes in the characteristics of the human""s visual system;
adapting the location and definition of the stimulus presentation to said transition zone according to said changes; and
reiterating the previous steps continuously so as to extend the human""s intact visual field into said transition zone and said transition zone into a zone of more deteriorated vision or a zone of less residual visual function or a zone of substantially complete visual system injury.
In a further embodiment, the invention relates to a device for training the visual system or vision of a human allowing the above training process to be conducted. The device essentially comprises
a central data processing means for recording, storing, processing and emitting data from the other means of the apparatus;
at least one visual stimuli emitting means;
a fixation point means allowing the fixation of the person""s view;
means for entering the person""s response on visual stimuli perceived;
means for allowing a control of said at least one optical stimuli presenting means in accordance with the performance of the person responding on optical stimuli perceived.
In a preferred embodiment of the invention, said device enables the steps of
locating and defining a zone of deteriorated vision or residual visual function or partial visual system injury (xe2x80x9ctransition zonexe2x80x9d) within the human""s visual system;
defining a training area which is located within said transition zone;
training the human""s visual system by presenting visual stimuli to the human""s visual system, the majority of said visual stimuli being presented in or near said transition zone;
recording changes in the characteristics of the human""s visual system;
adapting the location and definition of the stimulus presentation to said transition zone according to said changes; and
reiterating the previous steps continuously so as to extend the human""s intact visual field into said transition zone and said transition zone into a zone of more deteriorated vision or a zone of less residual visual function or a zone of substantially complete visual system injury.
Thus, the inherent feature of the present invention is that the training by stimulus presentation predominantly occurs in or near the zone of deteriorated vision or the zone of residual visual function or the zone of partial visual system injury, i. e. in the transition zone, which is the zone intended to be trained and a presentation of stimuli in the intact visual field is considerably reduced or even avoided. Thereby, the human""s vision can be improved much more efficiently than in the prior art.
With respect to these features, the present invention is different from the prior art process and device described by Kasten et al. (1997; loc. cit.) which does not disclose the continuous monitoring of the residual performance of the visual system of the person to be trained. Rather, the Kasten device keeps the training area of the visual field constant, stimulating over and over again areas where vision has already been restored or in which vision was not at all impaired. Thus, the prior art device presented stimuli independent upon the persons""actual performance. In said device, after experiencing some training benefit, the restored areas are still continuously being trained, even though this is no longer required. Thus, the visual presentation paradigm disclosed in the prior art is both laborious, time-consuming and in large part unnecessary. In fact, persons to be trained have reported that the prior art training is too long and boring.
In addition, with the prior art method it is not possible to detect and specifically treat areas of xe2x80x9conlyxe2x80x9d deteriorated vision or of residual visual functions or of partial visual system injury. Because of the time-consuming training, in the prior art process, including a training of areas or zones showing optimum results of visual performance, there has been a long-felt need to conceive of a optical stimulus presentation paradigm which is shorter in duration and more efficient in its use. In the present invention, we have therefore conceived a visual system training process and device by introducing the innovative step of continuously monitoring the performance of the person in need of a training of the visual field and stimulating only those regions of the visual system which are xe2x80x9conlyxe2x80x9d of deteriorated vision or partially injured.
Thus, in accordance with the present invention, we developed a more efficient approach by concentrating the visual stimulus presentations to those areas of the visual field in which a more efficient rehabilitation progress can be expected.
To overcome the limitation of the prior art devices, we now propose in accordance with the invention to first locate, define and characterize the zones of impaired, i. e. deteriorated vision or residual visual function or partial visual system injury. These zones of deteriorated vision or impaired vision or partial visual system injury are hereinafter shortly referred to as transition zones (see FIG. 1). Such transition zones may, for example, be found with aged people whose vision, for example lateral vision, becomes more and more restricted. Transition zones may also be found with people whose visual system was influenced as a result of a brain injury, stroke or similar event. Another example are transition zones between zones of completely maintained and wholly lost ability to visually discriminate between colours, shapes or movements. Within said transition zones, there are located the training areas or zones which are defined in the next step of the present procedure.
In a preferred embodiment of the invention, the size and location of said training area or areas within said transition zone are selected in accordance with the size, location and kind of the zone of partial visial system deterioration, of residual visual fimction or visual deficit of said human. In other words: It has to be checked carefully, which parts of the visual system of said human have the greatest need for the subsequent training by presenting optical stimuli.
Then, based on the individual person""s performance which is determined continuously or intermittently during said training, we propose to present the training stimuli in those transition zones. In preferred embodiments of the invention, optical and preferably light stimuli are presented to the person""s visual system. It is even more preferred that light stimuli of different colour, luminance, intensity and/or shape are presented to the visual system of the person to be trained. Such light stimuli can be presented as static light stimuli or a series of light stimuli in a sequence generating an impression of a moving object.
This xe2x80x9ctransition-zone based stimulus presentationxe2x80x9d is based on the consideration that there are areas of xe2x80x9conlyxe2x80x9d deteriorated vision of a person or partial visual functions where vision is neither intact nor completely damaged but where some neuronal structures survived the injury. It is reasoned that these surviving neurons, as long as their number exceeds a certain minimum (xe2x80x9chypothesis of minimal residual structurexe2x80x9d), mediate the return of vision due to training, and therefore their stimulation by training would be the critical step to be taken. As a consequence, to overcome the previously recognized problems of inefficient visual field stimulation, we therefore devised a new presentation strategy by selectively stimulating these regions (xe2x80x9ctransition zonesxe2x80x9d) using a computer-controlled stimulation device.
Specific algorithms were developed to follow the above presentation strategy, which algorithms allow the highly efficient training of areas of visual system dysfunction or malfunction. The detailed steps of the training procedure are described below with respect to stimulating specific areas or zones of the human visual system by optical stimuli.
During the training step, changes in the characteristics of the visual system of the human trained are recorded. In other words: The performance of the person trained in view of visually recognizing the optical stimuli presented and himself/herself presenting the desired reaction on said visual recognition step is recorded by the system/device of the present invention. To give just one example: The reaction time of the trained person on an optical stimulus presented to the transition zone of his/her visual system is measured, and the time elapsed between the emission of the optical stimulus and the reaction given (for example by pressing a button of the device), relative to an average time value measured before for the trained person as a base line value, is taken as the performance of the person with respect to the trained area of the transition zone. However, this example is not to be considered as limiting the invention; any other appropriate step may be taken, too, in order to continuously or intermittently record changes in the characteristics of the human""s visual system.
Based on the continuous recordal of the changes in the characteristics as decribed above, the location and definition of the transition zone is adapted to said changes. This may also be conducted continuously or intermittently. In other words: Depending upon the performance of the trained person in processing the presented optical stimuli by the visual system, the transition zone is newly defined. Without wanting to be bound by the explanation, it can be assumed that, due to the effective training of the defined transition zone, the vision of the trained person is improved in said transition zone, for example by improving any deteriorated fimction of the visual system (e. g. peripheral vision, visual acuity, ability to discriminate between different colours, shapes, movement; reduction of squinting; increase of the visual angle) or improving residual visual functions or removing partial visual system injuries. As a result thereof, the transition zone becomes an intact area of the person""s visual system, and another part of the defective area may become (and is defined to be) a transition zone for another step or series of steps of training by presenting optical stimuli to said new transition zone of the human""s visual system (see also FIG. 1).
By reiterating the above-described steps, the human""s intact visual field is continuously extended into zones which were previously located and defined to be transition zones, and said transition zones are continuously extended into zones which previously were zones of deteriorated vision or zones of less residual visual function or zones of substantially complete visual system injury, i. e. defective zones (see FIG. 1).
Using this computer program-based training, we conducted two independent placebo-controlled clinical trials in humans suffering from CNS damage. While our process and device can be used for any disorder of the visual system without that the present study is to be considered as a limitation to such severe disorders, the persons trained and evaluated in the present study were those with visual cortex or optic nerve injury. We were able to show for the first time, in a strictly controlled clinical trial, a significant reduction of partial blindness by training the persons""visual system through repetitive stimulation of the visual field, when stimulating areas of residual functions or xe2x80x9ctransition zonesxe2x80x9d.
Training Software and Training Procedure
Training was carried out with a personal computer for use at home where persons to be trained practiced on a regular basis. The preferred embodiment of the present invention is daily training for 1 hr in a darkened room for an extended time period, as for example a 6-months period as employed in this test. However, any other training period may also prove efficacious.
As the prior art devices have been inefficient, a special algorithm was developed which produced on a monitor an emission of light stimuli effecting a repetitive visual stimulation of the transition zone located between the intact and damaged visual field sector of the human to be trained. In a first step, the xe2x80x9ctransition zonexe2x80x9d was located, defined and characterized. i.e. there occured a determination of the exact residual visual function in said transition zone with respect to location, size and kind.
After said first step, there was defined a training area which is located within said transition zone. Said training area is a region within the transition zone where a regeneration of the neuronal structures of the person""s visual system could be expected due to the results of the definition and characterization of the transition zone in the first step, e. g. due to the presence of a minimum of remaining neuronal structures.
In a subsequent step, there was conducted a stimulation of the area of impaired function based on the performance determined in the first and second steps. This approach is more efficient because it does not stimulate intact areas of the visual field but just those areas which are characterized by impaired functions.
Also, unlike prior art devices in which the program only stores the data for a later analysis, the present invention adapts, on a continuous or intermittent basis, training algorithms to the visual system performance in or near the areas of impaired functions.
In addition, daily therapy results can be stored on suitable storing media like a tape or a disc which permits monitoring of compliance and which allows the therapy strategy to be adapted to the progress of the person.